Thrombin is a serine protease present in blood plasma in the form of a precursor, prothrombin. Thrombin plays a central role in the mechanism of blood coagulation by converting the solution plasma protein, fibrinogen, into insoluble fibrin.
Edwards et al., J. Amer. Chem. Soc., (1992) vol. 114, pp. 1854-63, describes peptidyl a-ketobenzoxazoles which are reversible inhibitors of the serine proteases human leukocyte elastase and porcine pancreatic elastase.
European Publication 363 284 describes analogs of peptidase substrates in which the nitrogen atom of the scissile amide group of the substrate peptide has been replaced by hydrogen or a substituted carbonyl moiety.
Australian Publication 86245677 also describes peptidase inhibitors having an activated electrophilic ketone moiety such as fluoromethylene ketone or a-keto carboxyl derivatives.
R. J. Brown et al., J. Med. Chem., Vol. 37, pages 1259-1261 (1994) describes orally active, non-peptidic inhibitors of human leukocyte elastase which contain trifluoromethylketone and pyridinone moieties.
H. Mack et al., J. Enzyme Inhibition, Vol. 9, pages 73-86 (1995) describes rigid amidino-phenylalanine thrombin inhibitors which contain a pyridinone moiety as a central core structure.
The invention includes compounds for inhibiting loss of blood platelets, inhibiting formation of blood platelet aggregates, inhibiting formation of fibrin, inhibiting thrombus formation, and inhibiting embolus formation in a mammal, comprising a compound of the invention in a pharmaceutically acceptable carrier. These compounds may optionally include anticoagulants, antiplatelet agents, and thrombolytic agents. The compounds can be added to blood, blood products, or mammalian organs in order to effect the desired inhibitions. The invention also includes a compound for preventing or treating unstable angina, refractory angina, myocardial infarction, transient ischemic attacks, atrial fibrillation, thrombotic stroke, embolic stroke, deep vein thrombosis, disseminated intravascular coagulation, ocular build up of fibrin, and reocclusion or restenosis of recanalized vessels, in a mammal, comprising a compound of the invention in a pharmaceutically acceptable carrier. These compounds may optionally include anticoagulants, antiplatelet agents, and thrombolytic agents.
The invention also includes a method for reducing the thrombogenicity of a surface in a mammal by attaching to the surface, either covalently or noncovalently, a compound of the invention.
The invention is a compound selected from the group consisting of: 
or a pharmaceutically acceptable salt thereof, wherein
T is selected from the group consisting of 
D, E, F, G, H, I, and J are independently N or CY1 provided that the number of such variables D, E, F, G, H, I, and J representing N is 0, 1, or 2;
K, L, M and Q are independently NH or CY1Y2, provided that the number of such variables D, E, F, K, L, M, and Q representing N is 0, 1, or 2;
Y1 and Y2 are independently selected from the group consisting of
hydrogen,
C1-4alkyl,
halogen,
amino, or
hydroxy;
A is 
W is
hydrogen
R1,
R1OCO,
R1CO,
R1SO2,
R1(CH2)nNHCO,
wherein n is 0-4;
R1 is
R2,
R2(CH2)mC(R12)2, where m is 0-3, and each R12 can be the same or different,
(R2)(OR2)CH(CH2)p, where p is 1-4, 
where m is 0-3,
R2C(R12)2(CH2)m, wherein m is 0-3, and each R12 can be the same or different, wherein (R12)2 can also form a ring with C represented by C3-7 cycloalkyl,
R2CH2C(R12)2(CH2)q, wherein q is 0-2, and each R12 can be the same or different, wherein (R12)2 can also form a ring with C represented by C3-7 cycloalkyl,
(R2)2CH(CH2)r, where r is 0-4 and each R2 can be the same or different, and wherein (R2)2 can also form a ring with CH represented by C3-7 cycloalkyl, C7-12 bicylic alkyl, C10-16 tricylic alkyl, or a 5- to 7-membered mono- or bicyclic heterocyclic ring which can be saturated or unsaturated, and which contains from one to three heteroatoms selected from the group consisting of N, O and S,
R2(CH2)tO(CH2)p, wherein t is 0 or 1 and p is 1-4,
R2CF2C(R12)2, 
(R2CH2)(R2CH2)Nxe2x80x94,
(R2CH2)(R2CH2)CH, or
R2(COOR3)(CH2)r, where r is 1-4;
R2 and R4 are independently
phenyl, unsubstituted or substituted with one or more of C1-4 
alkyl, C1-4 alkoxy, halogen, hydroxy, COOH, CONH2, CH2H, CO2Rxe2x80x2, where Rxe2x80x2 is C1-4 alkyl, or SO2NH2,
naphthyl,
biphenyl,
pyridine N-oxide,
a 5- to 7-membered mono- or a 9- to 10-membered bicyclic
a) non-heterocyclic ring system, which is saturated or unsaturated, and which is unsubstituted or substituted with halogen or hydroxy, or
b) heterocyclic ring system, which is saturated or unsaturated, having carbon ring atoms and heteroatom ring atoms, wherein the ring system contains i) from one to four heteroatoms selected from the group consisting of N, O, and S, and wherein the ring system is unsubstituted, or ii) from one to four nitrogen atoms, wherein one or more of the carbon and nitrogen ring atoms are substituted with halogen or hydroxy.
C1-7 alkyl, unsubstituted or substituted with one or more of hydroxy,
COOH,
amino,
aryl,
C3-7 cycloalkyl,
CF3,
N(CH3)2,
xe2x80x94C1-3alkylaryl,
heteroaryl, or
heterocycloalkyl,
CF3 
C3-7 cycloalkyl, unsubstituted or substituted with aryl,
C7-12 bicyclic alky, or
C10-16 tricyclic alkyl;
R3, R5 and R6are independently selected from the group consisting of
hydrogen,
halogen,
C1-4 alkyl,
C3-7 cycloalkyl, or
trifluoromethyl;
X is
hydrogen, or
halogen;
Z is CH2, S, or SO2;
R12 is
hydrogen,
phenyl, unsubstituted or substituted with one or more of C1-4 alkyl, C1-4 alkoxy, halogen, hydroxy, COOH, CONH2,
naphthyl,
biphenyl,
a 5- to 7-membered mono- or a 9- to 10-membered bicyclic heterocyclic ring which can be saturated or unsaturated, and which contains from one to four heteroatoms selected from the group consisting of N, O and S,
C1-4 alkyl, unsubstituted or substituted with one or more of hydroxy,
OH,
COOH,
amino,
xe2x80x94N(CH3)2,
xe2x80x94NH(CH3),
xe2x80x94N(CH2)COOH,
aryl,
heteroaryl, or
heterocycloalkyl,
CF3 
C3-7 cycloalkyl,
C7-12 bicyclic alkyl, or
C10-16 tricyclic alkyl.
In one class of compounds of the invention, Y1 and Y2 are hydrogen or amino. In a subclass of this class of compounds, A is 
In a group of this subclass, R5 and R6 are independently selected from xe2x80x94CH(CH3)2 and xe2x80x94CH2CH3, and W is selected from the group consisting of: 
Examples of this group are listed below. Inhibitory activity of compounds of the invention is represented by xe2x80x9c**xe2x80x9d indicating Ki greater than or equal to 20 nM, or xe2x80x9c*xe2x80x9d, indicating Ki less than 20 nM. Values are as determined according to the in vitro assay described later in the specification. 
The term xe2x80x9calkylxe2x80x9d means branched or straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms (for example, xe2x80x9cC1-10xe2x80x9d denotes alkyl having 1 to 10 carbon atoms, e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, iso-amyl, hexy, octyl radicals and the like.
The term xe2x80x9calkenylxe2x80x9d means hydrocarbon chains of either a straight of branched configuration and one or more unsaturated carbonxe2x80x94carbon bonds which may occur at an stable point along the chain, e.g., propylenyl, buten-1-yl, isobutenyl, pentenylen-1-yl, 2,2-methylbuten-1-yl, 3-methylbuten-1-yl, hexen-1-yl, hepten-1-yl, and octen-1-yl radicals and the like.
The term, xe2x80x9calkynylxe2x80x9d means hydrocarbon chains of either a straight or branched configuration and one or more triple carbon-carbon bonds which may occur in any stable point along the chain, e.g., ethynyl, propynyl, butyn-1-yl, butyn-2-yl, pentyn-1-yl, pentyn-2-yl, 3-methylbutyn-1-yl, hexyn-1-yl, hexyn-2-yl, hexyn-3-yl, 3,3-dimethylbutyn-1-yl radicals and the like.
The term xe2x80x9calkoxyxe2x80x9d means an alkyl group of indicated number of carbon atoms attached through an oxygen bridge, e.g., methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, pentyloxy, radicals and the like.
The terms xe2x80x9calkylenexe2x80x9d, xe2x80x9calkenylenexe2x80x9d, xe2x80x9cphenylenexe2x80x9d, and the like, refer to alkyl, alkenyl, and phenyl groups, respectively, which are connected by two bonds to the rest of the structure. Such xe2x80x9calkylenexe2x80x9d, xe2x80x9calkenylenexe2x80x9d, xe2x80x9cphenylenexe2x80x9d, and the like, may alternatively and equivalently be denoted herein as xe2x80x9cxe2x80x94(alkyl)xe2x80x94xe2x80x9d, xe2x80x9cxe2x80x94(alkenyl)xe2x80x94xe2x80x9d and xe2x80x9cxe2x80x94(phenyl)xe2x80x94xe2x80x9d, and the like.
The term xe2x80x9chalogenxe2x80x9d includes fluorine, chlorine, iodine and bromine.
The term xe2x80x9coxyxe2x80x9d means an oxygen (O) atom.
The term xe2x80x9cthioxe2x80x9d means a sulfur (S) atom.
The term xe2x80x9carylxe2x80x9d means a partially saturated or fully saturated 6-14 membered ring system such as for example, phenyl, naphthyl or anthracyl. The term xe2x80x9cPhxe2x80x9d, which appears in certain chemical formulas in the specification and claims, represents phenyl.
The term xe2x80x9ccycloalkylxe2x80x9d means saturated ring groups, including mono-, bi-, or poly-cyclic ring systems such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexy, cycloheptyl, cyclooctyl, adamantyl, and the like.
The term xe2x80x9cheterocyclicxe2x80x9d or xe2x80x9cheterocyclexe2x80x9d means a stable 5- to 7-membered monocyclic or bicyclic or 7- to 10-membered bicyclic heterocyclic ring which may be saturated, partially unsaturated, or fully unsaturated, which consists of carbon atoms and from 1 to 4 heteroatoms independently selected from the group consisting of N, O and S and wherein the nitrogen and sulfur heteroatoms may optionally be oxidized, and the nitrogen may optionally be quaternized, and including any bicyclic group in which any of the above-defined heterocyclic rings is fused to a benzene ring. The heterocyclic ring may be attached to its pendant group at any heteroatom or carbon atom which results in a stable structure. The heterocyclic rings described herein may be substituted on carbon or on a nitrogen atom if the resulting compound is stable. Examples of heterocyclic rings include, but are not limited to, pyridyl (pyridinyl), pyrimidinyl, furanyl (furyl), thiazolyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, tetrazolyl, benzofuranyl, benzothiophenyl, indolyl, indolenyl, isoxazolinyl, quinolinyl, isoquinolinyl, benzimidazolyl, piperidinyl, 4-piperidonyl, pyrrolidinyl, 2-pyrrolidonyl, pyrrolinyl, tetrahydrofuranyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl or octahydroisoquinolinyl, azocinyl, triazinyl, 6H-1,2,5-thiadiazinyl, 2H,6H-1,5,2-dithiazinyl, thianthrenyl, pyranyl, isobenzofuranyl, chromenyl, xanthenyl, phenoxanthiinyl, 2H-pyrrolyl, pyrrolyl, imidazolyl, pyrazolyl, isothiazolyl, isoxazolyl, oxazolyl, pyrazinyl, pyridazinyl, indolizinyl, isoindolyl, 3H-indolyl, 1H-indazolyl, purinyl, 4H-quinolizinyl, phthalazinyl, naphthyridinyl, quinoxalinyl, quinazolinyl, cinnolinyl, pteridinyl, 4aH-carbazole, carbazole, xcex2-carbolinyl, phenanthridinyl, acridinyl, perimidinyl, phenanthrolinyl, phenazinyl, phenarsazinyl, phenothiazinyl, furazanyl, phenoxazinyl, isochromanyl, chromanyl, imidazolidinyl, imidazolinyl, pyrazolidinyl, pyrazolinyl, piperazinyl, indolinyl, isoindolinyl, quinuclidinyl, morpholinyl or oxazolidinyl. Also included are fused ring and spiro compounds containing, for example, the above heterocycles.
The term xe2x80x9cheteroarylxe2x80x9d means an unsaturated heterocyclic group, preferably 5 or 6-membered monocyclic ring systems or 8-10 membered fused bicyclic groups, having heteroatoms selected from the group consisting of N, O, and S, for example, pyridyl (pyridinyl), pyrimidinyl, furanyl (furyl), thiazolyl, thienyl, pyrrolyl, pyrazolyl, imidazolyl, indolyl, isoxazolyl, oxazolyl, pyrazinyl, pyridazinyl, benzofuranyl, benzothienyl, benzimidazolyl, quinolinyl, or isoquinolinyl.
Under standard nonmenclature used throughout this disclosure, the terminal portion of the designated side chain is described first followed by the adjacent functionality toward the point of attachment. For example, a methylene substituted with ethylcarbonylamino is equivalent to 
Compounds of the present invention may be chiral; included within the scope of the present invention are racemic mixtures and separated enantiomers of the general formula. Furthermore, all diastereomers, including E, Z isomers, of the general formula are included in the present scope. Furthermore, hydrates as well as anhydrous compositions and polymorphs of the general formula are within the present invention. Thus, the term xe2x80x9cactive drugxe2x80x9d includes a compound of the invention and its salts, racemic mixtures or separated enantiomers, hydrates or anhydrous forms, polymorphs, and pharmaceutically acceptable salts.
The term xe2x80x9cpharmaceutically acceptable saltsxe2x80x9d shall mean non-toxic salts of the compounds of this invention which are generally prepared by reacting the free base with a suitable organic or inorganic acid. Representative salts include the following salts: acetate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, calcium edetate, camsylate, carbonate, chloride, clavulanate, citrate, dihydrochloride, edetate, edisylate, estolate, esylate, fumarate, gluceptate, gluconate, glutamate, glycollylarsanilate, hexylresorcinate, hydrabamine, hydrobromide, hydrochloride, hydroxynapthoate, iodide, isothionate, lactate, lactobionate, laurate, malate, maleate, mandelate, mesylate, methylbromide, methylnitrate, methylsulfate, mucate, napsylate, nitrate, oleate, oxalate, pamaote, palmitate, panthothenate, phosphate/diphosphate, polygalacturonate, salicylate, stearate, subacetate, succinate, tannate, tartrate, teoclate, tosylate, triethiodide, valerate.
Prodrugs, such as ester derivatives of active drug are compound derivatives which, when absorbed into the bloodstream of a warm-blooded animal, cleave in such a manner as to release the drug form and permit the drug to afford improved therapeutic efficacy.
The term xe2x80x9cpharmaceutically effective amountxe2x80x9d shall mean that amount of a drug or pharmaceutical agent that will elicit the biological or medical response of a tissue, system or animal that is being sought by a researcher or clinician. The term xe2x80x9canti-coagulantxe2x80x9d shall include heparin, and warfarin. The term xe2x80x9cthrombolytic agentxe2x80x9d shall include agents such as streptokinase and tissue plasminogen activator. The term xe2x80x9cplatelet anti-aggregation agentxe2x80x9d shall include agents such as aspirin and dipyridamole.
Some abbreviations that may appear in this application are as follows.
Assays of human a-thrombin and human trypsin were performed by the methods substantially as described in Thrombosis Research, Issue No. 70, page 173 (1993) by S. D. Lewis et al.
The assays were carried out at 25xc2x0 C. in 0.05 M TRIS buffer pH 7.4, 0.15 M NaCl, 0.1% PEG. Trypsin assays also contained 1 mM CaCl2. In assays wherein rates of hydrolysis of a p-nitroanilide (pna) substrate were determined, a Thermomax 96-well plate reader was used was used to measure (at 405 nm) the time dependent appearance of p-nitroaniline. sar-PR-pna was used to assay human a-thrombin (Km=125 xcexcM) and bovine trypsin (Km=125 xcexcM). p-Nitroanilide substrate concentration was determined from measurements of absorbance at 342 nm using an extinction coefficient of 8270 cmxe2x88x921Mxe2x88x921.
In certain studies with potent inhibitors (Ki less than 10 nM) where the degree of inhibition of thrombin was high, a more sensitive activity assay was employed. In this assay the rate of thrombin catalyzed hydrolysis of the fluorogenic substrate Z-GPR-afc (Km=27 xcexcM) was determined from the increase in fluorescence at 500 nm (excitation at 400 nm) associated with production of 7-amino-4-trifluoromethyl coumarin. Concentrations of stock solutions of Z-GPR-afc were determined from measurements of absorbance at 380 nm of the 7-amino-4-trifluoromethyl coumarin produced upon complete hydrolysis of an aliquot of the stock solution by thrombin.
Activity assays were performed by diluting a stock solution of substrate at least tenfold to a final concentration xe2x89xa60.1 Km into a solution containing enzyme or enzyme equilibrated with inhibitor. Times required to achieve equilibration between enzyme and inhibitor were determined in control experiments. Initial velocities of product formation in the absence (Vo) or presence of inhibitor (Vi) were measured. Assuming competitive inhibition, and that unity is negligible compared Km/[S], [I]/e, and [I]/e (where [S], [I], and e respectively represent the total concentrations, of substrate, inhibitor and enzyme), the equilibrium constant (Ki) for dissociation of the inhibitor from the enzyme can be obtained from the dependence of Vo/Vi on [I] shown in equation 1.
Vo/Vi=1+[I]/Kixe2x80x83xe2x80x83(1) 
The activities shown by this assay indicate that the compounds of the invention are therapeutically useful for treating various conditions in patients suffering from unstable angina, refractory angina, myocardial infarction, transient ischemic attacks, atrial fibrillation, thrombotic stroke, embolic stroke, deep vein thrombosis, disseminated intravascular coagulation, and reocclusion or restenosis of recanalized vessels. The compounds of the invention are selective compounds, as evidenced by their inhibitory activity against human trypsin (represented by Ki), which is at least 1000 nM.
Thrombin Inhibitorsxe2x80x94Therapeutic Usesxe2x80x94Method of Using
Anticoagulant therapy is indicated for the treatment and prevention of a variety of thrombotic conditions, particularly coronary artery and cerebrovascular disease. Those experienced in this field are readily aware of the circumstances requiring anticoagulant therapy. The term xe2x80x9cpatientxe2x80x9d used herein is taken to mean mammals such as primates, including humans, sheep, horses, cattle, pigs, dogs, cats, rats, and mice.
Thrombin inhibition is useful not only in the anticoagulant therapy of individuals having thrombotic conditions, but is useful whenever inhibition of blood coagulation is required such as to prevent coagulation of stored whole blood and to prevent coagulation in other biological samples for testing or storage. Thus, the thrombin inhibitors can be added to or contacted with any medium containing or suspected of containing thrombin and in which it is desired that blood coagulation be inhibited, e.g., when contacting the mammal""s blood with material selected from the group consisting of vascular grafts, stents, orthopedic prosthesis, cardiac prosthesis, and extracorporeal circulation systems.
Compounds of the invention are useful for treating or preventing venous thromboembolism (e.g. obstruction or occlusion of a vein by a detached thrombus; obstruction or occlusion of a lung artery by a detached thrombus), cardiogenic thromboembolism (e.g. obstruction or occlusion of the heart by a detached thrombus), arterial thrombosis (e.g. formation of a thrombus within an artery that may cause infarction of tissue supplied by the artery), atherosclerosis (e.g. arteriosclerosis characterized by irregularly distributed lipid deposits) in mammals, and for lowering the propensity of devices that come into contact with blood to clot blood.
Examples of venous thromboembolism which may be treated or prevented with compounds of the invention include obstruction of a vein, obstruction of a lung artery (pulmonary embolism), deep vein thrombosis, thrombosis associated with cancer and cancer chemotherapy, thrombosis inherited with thrombophilic diseases such as Protein C deficiency, Protein S deficiency, antithrombin III deficiency, and Factor V Leiden, and thrombosis resulting from acquired thrombophilic disorders such as systemic lupus erythematosus (inflammatory connective tissue disease). Also with regard to venous thromboembolism, compounds of the invention are useful for maintaining patency of indwelling catheters.
Examples of cardiogenic thromboembolism which may be treated or prevented with compounds of the invention include thromboembolic stroke (detached thrombus causing neurological affliction related to impaired cerebral blood supply), cardiogenic thromboembolism associated with atrial fibrillation (rapid, irregular twitching of upper heart chamber muscular fibrils), cardiogenic thromboembolism associated with prosthetic heart valves such as mechanical heart valves, and cardiogenic thromboembolism associated with heart disease.
Examples of arterial thrombosis include unstable angina (severe constrictive pain in chest of coronary origin), myocardial infarction (heart muscle cell death resulting from insufficient blood supply), ischemic heart disease (local anemia due to obstruction (such as by arterial narrowing) of blood supply), reocclusion during or after percutaneous transluminal coronary angioplasty, restenosis after percutaneous transluminal coronary angioplasty, occlusion of coronary artery bypass grafts, and occlusive cerebrovascular disease. Also with regard to arterial thrombosis, compounds of the invention are useful for maintaining patency in arteriovenous cannulas.
Examples of atherosclerosis include arteriosclerosis.
Examples of devices that come into contact with blood include vascular grafts, stents, orthopedic prosthesis, cardiac prosthesis, and extracorporeal circulation systems.
The thrombin inhibitors of the invention can be administered in such oral forms as tablets, capsules (each of which includes sustained release or timed release formulations), pills, powders, granules, elixers, tinctures, suspensions, syrups, and emulsions. Likewise, they may be administered in intravenous (bolus or infusion), intraperitoneal, subcutaneous, or intramuscular form, all using forms well known to those of ordinary skill in the pharmaceutical arts. An effective but non-toxic amount of the compound desired can be employed as an anti-aggregation agent. For treating ocular build up of fibrin, the compounds may be administered intraocularly or topically as well as orally or parenterally.
The thrombin inhibitors can be administered in the form of a depot injection or implant preparation which may be formulated in such a manner as to permit a sustained release of the active ingredient. The active ingredient can be compressed into pellets or small cylinders and implanted subcutaneously or intramuscularly as depot injections or implants. Implants may employ inert materials such as biodegradable polymers or synthetic silicones, for example, Silastic, silicone rubber or other polymers manufactured by the Dow-Coming Corporation.
The thrombin inhibitors can also be administered in the form of liposome delivery systems, such as small unilamellar vesicles, large unilamellar vesicles and multilamellar vesicles. Liposomes can be formed from a variety of phospholipids, such as cholesterol, stearylamine or phosphatidylcholines.
The thrombin inhibitors may also be delivered by the use of monoclonal antibodies as individual carriers to which the compound molecules are coupled. The thrombin inhibitors may also be coupled with soluble polymers as targetable drug carriers. Such polymers can include polyvinlypyrrolidone, pyran copolymer, polyhydroxy-propyl-methacrylamide-phenol, polyhydroxyethyl-aspartamide-phenol, or polyethyleneoxide-polylysine substituted with palmitoyl residues. Furthermore, the thrombin inhibitors may be coupled to a class of biodegradable polymers useful in achieving controlled release of a drug, for example, polylactic acid, polyglycolic acid, copolymers of polylactic and polyglycolic acid, polyepsilon caprolactone, polyhydroxy butyric acid, polyorthoesters, polyacetals, polydihydropyrans, polycyanoacrylates and cross linked or amphipathic block copolymers of hydrogels.
The dosage regimen utilizing the thrombin inhibitors is selected in accordance with a variety of factors including type, species, age, weight, sex and medical condition of the patient; the severity of the condition to be treated; the route of administration; the renal and hepatic function of the patient; and the particular compound or salt thereof employed. An ordinarily skilled physician or veterinarian can readily determine and prescribe the effective amount of the drug required to prevent, counter, or arrest the progress of the condition.
Oral dosages of the thrombin inhibitors, when used for the indicated effects, will range between about 0.01 mg per kg of body weight per day (mg/kg/day) to about 30 mg/kg/day, preferably 0.025-7.5 mg/kg/day, more preferably 0.1-2.5 mg/kg/day, and most preferably 0.1-0.5 mg/kg/day (unless specificed otherwise, amounts of active ingredients are on free base basis). For example, an 80 kg patient would receive between about 0.8 mg/day and 2.4 g/day, preferably 2-600 mg/day, more preferably 8-200 mg/day, and most preferably 8-40 mg/kg/day. A suitably prepared medicament for once a day administration would thus contain between 0.8 mg and 2.4 g, preferably between 2 mg and 600 mg, more preferably between 8 mg and 200 mg, and most preferably 8 mg and 40 mg, e.g., 8 mg, 10 mg, 20 mg and 40 mg. Advantageously, the thrombin inhibitors may be administered in divided doses of two, three, or four times daily. For administration twice a day, a suitably prepared medicament would contain between 0.4 mg and 4 g, preferably between 1 mg and 300 mg, more preferably between 4 mg and 100 mg, and most preferably 4 mg and 20 mg, e.g., 4 mg, 5 mg, 10 mg and 20 mg.
Intravenously, the patient would receive the active ingredient in quantities sufficient to deliver between 0.025-7.5 mg/kg/day, preferably 0.1-2.5 mg/kg/day, and more preferably 0.1-0.5 mg/kg/day. Such quantities may be administered in a number of suitable ways, e.g. large volumes of low concentrations of active ingredient during one extended period of time or several times a day, low volumes of high concentrations of active ingredient during a short period of time, e.g. once a day. Typically, a conventional intravenous formulation may be prepared which contains a concentration of active ingredient of between about 0.01-1.0 mg/ml, e.g. 0.1 mg/ml, 0.3 mg/ml, and 0.6 mg/ml, and administered in amounts per day of between 0.01 ml/kg patient weight and 10.0 ml/kg patient weight, e.g. 0.1 ml/kg, 0.2 ml/kg, 0.5 ml/kg. In one example, an 80 kg patient, receiving 8 ml twice a day of an intravenous formulation having a concentration of active ingredient of 0.5 mg/ml, receives 8 mg of active ingredient per day. Glucuronic acid, L-lactic acid, acetic acid, citric acid or any pharmaceutically acceptable acid/conjugate base with reasonable buffering capacity in the pH range acceptable for intravenous administration may be used as buffers. Consideration should be given to the solubility of the drug in choosing an The choice of appropriate buffer and pH of a formulation, depending on solubility of the drug to be administered, is readily made by a person having ordinary skill in the art.
The compounds can also be administered in intranasal form via topical use of suitable intranasal vehicles, or via transdermal routes, using those forms of transdermal skin patches well known to those of ordinary skill in that art. To be administered in the form of a transdermal delivery system, the dosage administration will, or course, be continuous rather than intermittent throughout the dosage regime.
The thrombin inhibitors are typically administered as active ingredients in admixture with suitable pharmaceutical diluents, excipients or carriers (collectively referred to herein as xe2x80x9ccarrierxe2x80x9d materials) suitably selected with respect to the intended form of administration, that is, oral tablets, capsules, elixers, syrups and the like, and consistent with convention pharmaceutical practices.
For instance, for oral administration in the form of a tablet or capsule, the active drug component can be combined with an oral, non-toxic, pharmaceutically acceptable, inert carrier such as lactose, starch, sucrose, glucose, methyl cellulose, magnesium stearate, dicalcium phosphate, calcium sulfate, mannitol, sorbitol and the like; for oral administration in liquid form, the oral drug components can be combined with any oral, non-toxic, pharmaceutically acceptable inert carrier such as ethanol, glycerol, water and the like. Moreover, when desired or necessary, suitable binders, lubricants, distintegrating agents and coloring agents can also be incorporated into the mixture. Suitable binders include starch, gelatin, natural sugars such as glucose or beta-lactose, corn-sweeteners, natural and synthetic gums such as acacia, tragacanth or sodium alginate, carboxymethylcellulose, polyethylene glycol, waxes and the like. Lubricants used in these dosage forms include sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride and the like. Disintegrators include, without limitation, starch methyl cellulose, agar, bentonite, xanthan gum and the like.
Typical uncoated tablet cores suitable for administration of thrombin inhibitors are comprised of, but not limited to, the following amounts of standard ingredients:
Mannitol, microcrystalline cellulose and magnesium stearate may be substituted with alternative pharmaceutically acceptable excipients.
The thrombin inhibitors can also be co-administered with suitable anti-platelet agents, including, but not limited to, fibrinogen receptor antagonists (e.g. to treat or prevent unstable angina or to prevent reocclusion after angioplasty and restenosis), anticoagulants such as aspirin, thrombolytic agents such as plasminogen activators or streptokinase to achieve synergistic effects in the treatment of various vascular pathologies, or lipid lowering agents including antihypercholesterolemics (e.g. HMG CoA reductase inhibitors such as lovastatin, HMG CoA synthase inhibitors, etc.) to treat or prevent atherosclerosis. For example, patients suffering from coronary artery disease, and patients subjected to angioplasty procedures, would benefit from coadministration of fibrinogen receptor antagonists and thrombin inhibitors. Also, thrombin inhibitors enhance the efficiency of tissue plasminogen activator-mediated thrombolytic reperfusion. Thrombin inhibitors may be administered first following thrombus formation, and tissue plasminogen activator or other plasminogen activator is administered thereafter.
Typical doses of thrombin inhibitors of the invention in combination with other suitable anti-platelet agents, anticoagulation agents, or thrombolytic agents may be the same as those doses of thrombin inhibitors administered without coadministration of additional anti-platelet agents, anticoagulation agents, or thrombolytic agents, or may be substantially less that those doses of thrombin inhibitors administered without coadministration of additional anti-platelet agents, anticoagulation agents, or thrombolytic agents, depending on a patient""s therapeutic needs.
Schemes A through I outline general procedures for making intermediates having the general formula 
General Procedure for Making Compounds of the Invention
Compounds may be prepared, for example, by a common condensation reaction between a group having a carboxylic acid moiety and a group having an amino moiety, forming a peptide or amide bond. Compounds may be prepared by other means however, and suggested starting materials and procedures described below are exemplary only and should not be construed as limiting the scope of the invention.
In general, compounds having the general structure 
wherein the variables have the above-described meanings, can be prepared by reacting 
with an amino-containing intermediate selected from the group consisting of 
under conditions suitable for forming an amide bond between the acid and the amine.
Suitable carboxylic acid starting materials for 
may be prepared according to the following procedures.
Carboxylic Acids
Starting allylamine is condensed with acetaldehyde and cyanide in Step A to afford the aminonitrile. This is reacted in Step B with oxalyl chloride according to the method of Hoomaert [J. Heterocyclic Chem., 20, 919, (1983)] to give the pyrazinone. The olefin is oxidatively cleaved with ruthenium tetraoxide and the resulting aldehyde is converted to the acid by an oxidizing agent such as chromic acid in Step C. The 3-chloro group is then displaced by an ammonia equivalent, in this case p-methoxybenzylamine in Step D. The remaining chlorine is removed by reduction with Raney nickel in Step E and in Step F the p-methoxybenzyl group is removed by treatment with a strong acid such as TFA. 
Typically, solution phase amide couplings may be used to form the final product, but solid-phase synthesis by classical Merrifield techniques may be employed instead. The addition and removal of one or more protecting groups is also typical practice.
Modifications of the method will allow different W, R3, and X groups contemplated by the scope of the broad claim below to be present by the use of an appropriate reagent or appropriately substituted starting material in the indicated synthetic step. For example the starting aldehyde in Step A can have as its side chain, ethyl, isopropyl, cyclopropyl, trifluoromethyl, and the like, to achieve the different operable values of R3. Likewise, different W groups can be present by the use of an appropriate amine in Step D. Different X groups can be present by the omission of step E, and by the use of a reagent such as oxalyl bromide in step B. Obvious variations and modifications of the method to produce similar and obvious variants thereof, will be apparent to one skilled in the art.
The acid from METHOD 1, Step C is coupled to the appropriate amine. The 3-chloro group is then displaced by the appropriate amine and a protecting group is then removed, if necessary, to give the final product.
Modifications of the method will allow different W, R3, and X groups contemplated by the scope of the broad claim below to be present by the use of an appropriate reagent or appropriately substituted starting material in the indicated synthetic step. Obvious variations and modifications of the method to produce similar and obvious variants thereof, will be apparent to one skilled in the art.
An ester of glycine, in this case the benzyl ester, is condensed with acetaldehyde and cyanide in Step A to afford the aminonitrile. This is reacted in Step B with oxalyl chloride to give the pyrazinone. The 3-chloro group is then displaced by the appropriate amine, in this case phenethylamine, in Step C. The ester is hydrolyzed in Step D and the remaining chlorine is then removed by hydrogenolysis in Step E. 
Starting allylamine is condensed with acetaldehyde and cyanide in Step A to afford the aminonitrile. This is reacted in Step B with oxalyl chloride according to the method of Hoornaert [J. Heterocyclic Chem., 20, 919, (1983)] to give the pyrazinone. The olefin is oxidatively cleaved with ruthenium tetraoxide and the resulting aldehyde is converted to the acid by an oxidizing agent such as chromic acid in Step C. The 3-chloro group is then displaced by the appropriate amine, in this case phenethylamine, in Step D and the remaining chlorine is then removed by reduction with Raney nickel in Step E. 
Amide couplings to form the compounds of this invention can be performed by the carbodiimide method. Other methods of forming the amide or peptide bond include, but are not limited to the synthetic routes via an acid chloride, azide, mixed anhydride or activated ester. Typically, solution phase amide couplings are performed, but solid-phase synthesis by classical Merrifield techniques may be employed instead. The addition and removal of one or more protecting groups is also typical practice.
Modifications of the method will allow different W, R3, and X groups contemplated by the scope of the broad claim below to be present by the use of an appropriate reagent or appropriately substituted starting material in the indicated synthetic step. For example the starting aldehyde in Step A can have as its side chain, ethyl, isopropyl, cyclopropyl, trifluoromethyl, and the like, to achieve the different operable values of R3. Likewise, different W groups can be present by the use of an appropriate amine in Step D. Different X groups can be present by the omission of step E, and by the use of a reagent such as oxalyl bromide in step B. Obvious variations and modifications of the method to produce similar and obvious variants thereof, will be apparent to one skilled in the art.


Ethyl 2-pyridinoylformate (6-1).
To a stirred solution of 20 mL (210 mmol) of 2-bromopyridine in 500 mL of dry ether at xe2x88x9278xc2x0 C. under Ar was added 85 mL of a 2.5 M solution of n-butyllithium in hexane in a slow stream. After stirring in the cold for 30 min, the solution was transferred over a 5 min period via two cannula into a 0xc2x0 C. stirred solution of 100 mL (736 mmol) of diethyl oxalate in 1.0 L of dry ether under Ar. After stirring for 2 h in the cold, the reaction mixture was washed with 600 mL of sat. NaHCO3, water, and brine. The solution was dried over MgSO4 and the solvents concentrated at reduced pressure to give a red oil that was purified by SiO2 chromatography (10xc3x9715 cm) using 1:4 to 35:65 EtOAc-hexanes. The product-containing fractions were concentrated at reduced pressure to afford 6-1 as a reddish oil: 1H NMR (CDCl3) xcex4 1.42 (t, 3H), 4.45-4.55 (m, 2H), 7.55-7.6 (m, 1H), 7.9-7.95 (m, 1H), 8.11 (d, 1H), 8.78 (d, 1H).
Ethyl difluoro-2-pyridylacetate (6-2).
A stirred solution of 22 g (123 mmol) of ethyl 2-pyridinoylformate 6-1 and 75 g (465 mmol) of diethylaminosulfurtrifluoride (DAST) were heated to 55xc2x0 C. under Ar overnight. Because the reaction was not complete, 5 g additional DAST was added, and the reaction heated for an additional 24 h. The reaction mixture was cooled to rt, and poured very slowly into a stirred mixture of 1 kg of ice, 400 mL of ethyl acetate and 500 mL of sat. NaHCO3. After the addition, the mixture was basified by the addition of solid NaHCO3. The aqueous layer was extracted with EtOAc, and the combined organic layers washed with sat. NaHCO3, brine, dried over Na2SO4 and the solvents concentrated at reduced pressure to give 6-2 as a brown oil: 1H NMR (CDCl3) xcex41.35 (t, 3H), 4.35-4.4 (m, 2H), 7.4-7.45 (m, 1H), 7.75 (d, 1H), 7.95 (d, 1H), 8.45 (d, 1H).
2,2-Difluoro-2-(2-pyridyl)ethanol (6-3).
To a stirred solution of 19.5 g (97 mmol) of ethyl difluoro-2-pyridylacetate 6-2 in 200 mL of absolute ethanol at 0xc2x0 C. was added 4.42 g (116 mmol) of sodium borohydride in small portions. After 30 min, the reaction was quenched by the addition of 50 mL of sat. NH4Cl. The reaction mixture was concentrated at reduced pressure and the residue partitioned between 500 mL of ethyl acetate and sat. NaHCO3. The organic layer was washed with water, brine, and dried over Na2SO4 and concentrated at reduced pressure to give a brown oil that was purified on SiO2 (10xc3x9717 cm) using 1:1 EtOAc-hexane. After re-chromatographing the mixed fractions, all clean fractions were combined and concentrated at reduced pressure, giving 6-3 as a beige crystalline solid: 1H NMR (CDCl3) xcex4 3.6 (t, 1H), 4.17-4.3 (m, 2H), 7.4-7.45 (m, 1H), 7.73 (d, 1H), 7.84-7.91 (m, 1H ), 8.61 (d, 1H).
2,2-Difluoro-2-(2-pyridyl)ethyl trifluoromethanesulfonate (6-4).
To a stirred solution of 5 g (31.4 mmol) of 2,2-difluoro-2-(2-pyridyl)ethanol 6-3 and 9.69 g (47.2 mmol) of 2,6-di-t-butyl-4-methylpyridine in 110 mL of methylene chloride at xe2x88x9278xc2x0 C. under Ar was added 7.93 mL (47.2 mmol) of triflic anhydride dropwise. After 1 h, the reaction was diluted with 100 mL of pentane and filtered. The filtrate was concentrated and treated again with pentane and filtered. Concentration of the filtrate gave 6-4 as a brown oil, contaminated with 2,6-di-t-butyl-4-methylpyridine: 1H NMR (CDCl3) xcex4 5.12 (t, 2H), 7.45-7.5 (m, 1H), 7.75 (d, 1H), 7.86-7.94 (m, 1H), 8.65 (d, 1H).
2,2-Difluoro-2-(2-pyridyl)ethylazide (6-5).
To a stirred solution of 5.5 g of 2,2-difluoro-2-(2-pyridyl)ethyl trifluoromethanesulfonate 6-4 in 70 mL of DMF was added 6.74 g (104 mmol) of sodium azide under Ar. The mixture was heated to 60xc2x0 C. overnight. A second batch was run in the same manner, and after cooling to rt, both reactions were poured into 600 mL of water, and extracted with 3xc3x97500 mL of ether. The combined extracts were washed with brine, dried over Na2SO4 and concentrated at reduced pressure to give an oil that was purified by SiO2 (10xc3x976 cm) using hexane 1:3 EtOAc-hexane and 1:1 EtOAc-hexane. The product-containing fractions were concentrated at reduced pressure to give 6-5 as a yellow oil: 1H NMR (CDCl3) xcex4 4.05 (t, 2H), 7.4-7.45 (m, 1H), 7.73 (d, 1H), 7.83-7.89 (m, 1H), 8.67 (d, 1H).
2,2-Difluoro-2-(2-pyridyl)ethylamine (6xe2x80x946).
A stirred solution of 100 mg of 2,2-difluoro-2-(2-pyridyl)ethylazide 6xe2x80x946 was hydrogenated in 10 mL of ethyl acetate over 100 mg of 10% palladium on carbon using a balloon for 1 h. The catalyst was removed by filtration and the solvents removed at reduced pressure. A total of 1.8 g (9.7 mmol) of the azide was reduced using this procedure to give 6xe2x80x946 as a yellow oil: 1H NMR (CDCl3) 67  8.66 (d, 1H, 4.2 Hz), 7.82 (td, 1H, 7.7, 1.7 Hz), 7.68 (d, 1H, 8.1 Hz), 7.37-7.40 (m, 1H), 3.44 (t, 2H, 14.3 Hz), 1.41 (br s, 2H).
Ethyl 3-(2,2-difluoro-2-(2-pyridylethylamino)-6-methylpyrazin(1H)-2-one-1-acetate (6-7). A solution of 7.13 g (45.1 mmol) of 2,2-difluoro-2-(2-pyridyl)ethylamine and 12.4 g (45.1 mmol) of ethyl 3-bromo-6-methylpyrazin(1H)-2-one-1-acetate was heated to 125xc2x0 C. in a sealed tube overnight in 15 mL of toluene and 15 mL of ethanol. The reaction was concentrated and the residue was diluted with ethyl acetate, washed with 15% NaHCO3 and the aqueous layer backwashed with 3 portions of ethyl acetate. The combined organic layers were dried over MgSO4 and the solvents removed at reduced pressure to give an oil that was chromatographed on SiO2 using 50:50 hexane-EtOAc to give the title compound as a pale yellow solid: 1H NMR (CDCl3) xcex4 8.67 (d, 1H, 4.8 Hz), 7.80 (t, 1H, 7.9 Hz), 7.68 (d, 1H, 7.9 Hz), 7.36-7.39 (m, 1H), 6.71 (s, 1H), 6.31 (br t, 1H), 4.69 (s, 2H), 4.35 (td, 2H, 14.1, 6.6 Hz), 4.24 (q, 2H, 7.1 Hz), 2.11 (s, 3H), 1.29 (t, 3 H, 6.8 Hz).
3-(2,2-Difluoro-2-(2-pyridylethylamino)-6-methylpyrazin(1H)-2-one-1-acetic acid (6-8).
To a stirred solution of 9.67 g (27.5 mmol) of ethyl 3-(2,2-difluoro-2-(2-pyridylethylamino)-6-methylpyrazin(1H)-2-one-1-acetate in 100 mL of methanol was added 8.58 g (153.0 mmol) of potassium hydroxide in 20 mL of water. After 1 h, the solution was concentrated at reduced pressure, and the residue dissolved in 25 mL of water. This solution was acidified to pH=7 using 1.3 M HCl, and concentrated at reduced pressure to give a yellow solid containing potassium chloride and the title compound: 1H NMR (CD3OD) 67  8.65 (d, 1H, 4.7 Hz), 7.95 (td, 1H, 7.9, 1.8 Hz), 7.72-7.74 (m, 1H), 7.50-7.54 (m, 1H), 6.64 (d, 1H, 1.09 Hz), 4.78 (s, 2H), 4.31 (t, 2H, 14.1 Hz), 2.16 (s, 3H).

Ethyl N-(ethyl carboxymethyl)oxamate (7-1)
To a suspension of ethyl glycinexe2x80xa2HCl (38.4 g, 275 mmol) in 1,2-dichloroethane (360 mL) was added triethylamine (77.0 mL, 550 mmol) at room temperature. After stirring for 30 minutes the heterogenous mixture was cooled to 0xc2x0 C. and ethyl oxalyl chloride (30.3 mL, 275 mol) was added dropwise over the course of 1 h. Upon completion of the addition, the cooling bath was removed and the reaction was stirred at room temperature overnight. The reaction was diluted with water (250 mL) and the layers separated. The aqueous layer was backwashed with 2 portions of dichloromethane (250 mL). The combined organic layers were washed with water (250 mL), followed by brine (250 mL), dried over MgSO4 and concentrated to give an oil 7-1 that was taken directly onto the next step.
N-(Ethyl carboxymethyl)-Nxe2x80x2-(2,2-dimethoxyethyl)oxamide (7-2)
To a solution of the oxamate (84.0 g, 414 mmol) 7-1 in 2-propanol (500 mL) was added aminoacetaldehyde dimethyl acetal (45.7 g, 435 mmol) in one portion. After stirring overnight at room temperature, the reaction mixture was concentrated to a thick orange oil. This thick slurry was diluted with 2-propanol (300 mL) and the solid was broken up with a spatula. Filtration afforded a solid which was further rinsed with an additional portion of 2-propanol. Removal of residual 2-propanol was accomplished via high vacuum to afford a light orange solid 7-2. (89.8 g): 1H NMR (CDCl3) xcex4 7.82 (br s, 1H), 7.50 (br s, 1H), 4.41 (t, 1H, 5.3 Hz), 4.24 (q, 2H, 7.1 Hz), 4.09 (d, 2H, 5.9 Hz), 3.47 (dd, 2H, 5.3, 6.2 Hz), 3.40 (s, 6H), 1.30 (t, 3 H, 7.1 Hz).
Ethyl 3-hydroxypyrazin(1H)-2-one-1-acetate (7-3)
A solution of the oxamide (89.8 g, 343 mmol) 2xe2x80x942, acetic acid (400 mL), and conc. HCl (2 mL) was heated to reflux. After 1 h the black reaction was concentrated to a thick oil (high vacuum employed to ensure complete removal of AcOH) which was diluted with EtOH (150 mL) and MeOH (150 mL). Scraping the thick black oil with a spatula induced precipitation of the product. The MeOH was removed via rotary evaporation and the remaining slurry was filtered and rinsed with EtOH (200 mL) to deliver a tan solid. Recrystallization from refluxing EtOH (300 mL) afforded an off-white powder 7-3: 1H NMR (CD3OD) xcex4 6.50 (d, 1H, 5.9 Hz), 6.36 (d, 1H, 5.9 Hz), 4.58 (s, 2H), 4.23 (q, 2H, 7.1 Hz), 1.28 (t, 3H, 7.1 Hz). Further crude dione could be obtained upon concentration of the mother liquor.
Ethyl 3-bromopyrazin(1H)-2-one-1-acetate (7-4)
A solution of the hydroxypyrazinone (25.0 g, 126 mmol) 7-3 and phosphorous oxybromide (37.9 g, 132 mmol) in 1,2-dichloroethane (250 mL) was heated to reflux. After 8 h the reaction mixture was treated with sat. aq. Na2CO3 (250 mL) and stirred for 1h. The mixture was diluted with water (100 mL) and dichloromethane (100 mL), the layers were separated and the aqueous layer was backwashed with EtOAc (3xc3x97200 mL). The combined organics were dried (MgSO4), and concentrated to give an oil which was stored on a high vacuum line overnite to afford brown solid 7-4: 1H NMR (CDCl3) xcex4 7.17 (d, 1H, 4.2 Hz), 7.07 (d, 1H, 4.2 Hz), 4.65 (s, 2H), 4.27 (q, 2H, 7.2 Hz), 1.31 (t, 3H, 7.2 Hz).
Ethyl 3-(2,2-difluoro-2-(2-pyridylethylamino)pyrazin(1H)-2-one-1-acetate (7-5)
A solution of 4.80 g (30.4 mmol) of 2,2-difluoro-2-(2-pyridyl)ethylamine, 4.24 mL (30.4 mmol) of triethylamine and 7.93 g (30.4 mmol) of ethyl 3-bromopyrazin(1H)-2-one-1-acetate 2-4 was heated to 120xc2x0 C. in a sealed tube overnight in 12 mL of toluene and 4 mL of ethanol. The reaction was concentrated and the residue was partitioned between dichloromethane and sat. aq. NaHCO3. The aqueous layer was backwashed with 4 portions of dichloromethane. The combined organic layers were dried over MgSO4 and the solvents removed at reduced pressure to give an oil that was chromatographed on SiO2 using 60:40 to 40:60 hexane-EtOAc to give 7-5 as a yellow solid: 1H NMR (CDCl3) xcex4 8.67 (dd, 1H, 4.8, 0.7 Hz), 7.81 (ddd, 1H, 7.8, 7.8, 1.7 Hz), 7.69 (dd, 1H, 7.8, 1 Hz), 7.38 (dd, 1H, 5.1, 7.0 Hz), 6.86 (d, 1H, 4.8 Hz), 6.54 (br t, 1H, 5.9 Hz), 6.40 (d, 1H, 4.6 Hz), 4.54 (s, 2H), 4.38 (td, 2H, 14.0, 6.4 Hz), 4.24 (q, 2H, 7.1 Hz), 1.29 (t, 3H, 7.1 Hz).
Ethyl 3-(2,2-difluoro-2-(2-pyridylethylamino)-6-chloropyrazin(1H)-2-one-1-acetate (7-6)
To a stirred solution of 6.81 g (20.1 mmol) of ethyl 3-(2,2-difluoro-2-(2-pyridylethylamino)pyrazin(1H)-2-one-1-acetate 2-5 and 2.42 g (18.1 mmol) of N-chlorosuccinimide in 100 mL of 1,2-dichloroethane was heated to reflux. An additional 242 mg (1.81 mmol) and 75 mg (0.56 mmol) of NCS were added to the reaction mixture after 1 h and 1.5 h, respectively. After 2.5 h total, the solution was cooled to room temperature and partitioned between dichloromethane (150 mL) and sat. aq. NaHCO3 (200 mL). The layers were separated and the aqueous phase was backwashed with dichloromethane (2xc3x97200 mL). The combined organic layers were dried over MgSO4 and the solution concentrated to a volume of 10 mL. This liquid was directly loaded onto a SiO2 column and eluted with 65:35 to 55:45 hexane-EtOAc to give 7-6 as a yellow solid: 1H NMR (CDCl3) xcex4 8.68 (d, 1H, 4.8, Hz), 7.83 (ddd, 1H, 7.7, 7.7, 1.6 Hz), 7.9 (dd, 1H, 7.9 Hz), 7.40 (dd, 1H, 4.9, 7.3 Hz), 6.96 (s, 1H), 6.49 (br t, 1H, 5.9 Hz), 4.89 (s, 2H), 4.38 (td, 2H, 13.9, 6.5 Hz), 4.26 (q, 2H, 7.1 Hz), 1.30 (t, 3H, 7.1 Hz). 3-(2,2-Difluoro-2-(2-pyridylethylamino)-6-chloropyrazin(1H)-2-one-1-acetic acid (7-7)
To a stirred solution of 7.27 g (19.5 mmol) of ethyl 3-(2,2-difluoro-2-(2-pyridylethylamino)-6-chloropyrazin(1H)-2-one-1-acetate 7-6 in 200 mL of methanol was added 39 mL (39.0 mmol) of IM aq. potassium hydroxide. After 3 h the solution was acidified to pH=7 using conc. HCl, and concentrated at reduced pressure (azeotrope with PhCH3) to give a white solid containing potassium chloride and 7-7: 1H NMR (CDl3) xcex48.64 (d, 1H, 4.8 Hz), 7.93 (ddd, 1H, 7.7, 7.7, 1.5 Hz), 7.70 (d, 1H, 8.0 Hz), 7.49 (dd, 1H, 5.2, 7.4 Hz), 6.80 (s, 1H), 4.67 (s, 2H), 4.27 (t, 2H, 13.9 Hz).

To a solution 9 g (33 mmol) of ethyl 3-bromo-6-methylpyrazin-2-one-1-acetate (see Sanderson et al., WO 99/11267, compound 7-4, pages 34-37 the contents of which are hereby incorporated by reference, referenced above as compound xe2x80x9cAxe2x80x9d) was added 6 mL (50 mmol) 2-(2-pyridyl)ethylamine in 5 mL ethanol and the solution was heated to reflux for 48 hrs. The reaction mixture was diluted with 800 mL EtOAc, washed with 750 mL each of saturated aqueous sodium bicarbonate solution, water, and brine, then dried over Na2SO4, filtered and concentrated. Crystallization from 400 mL of 3:1 hexane:EtOAc gives ethyl 3-(2-(2-pyridyl)ethylamino)-6-methylpyrazin-2-one-1-acetate. Treatment of 2 g(6.3 mmol) of this in 20 mL MeOH with 5 mL (0.66 mmol, 1.32M aqueous solution) LiOH for 3 hours followed by addition of 0.52 L (0.66 mmol, 12N aqueous solution) HCl and filtration afforded 3-(2-(2-pyridyl)ethylamino)-6-methylpyrazin-2-one-1-acetic acid.: 1H NMR (CD3OD) xcex4 8.49 (d, 1H, J=4.3 Hz); 7.83 (dt, 1H, J=7.77 and 1.74 Hz); 7.42 (d, 1H, J=7.86 Hz); 7.33 (m, 111); 6.66 (s, 1H); 4.70 (s, 2H); 3.72 (t, 2H, J=6.95 Hz); 3.12 (t, 2H, J=6.95 Hz); 2.16 (s, 3H).
Suitable carboxylic acid starting materials for 
may be prepared according to the following procedures.
General Synthesis 
Step A: Ethyl 6-methyl-3-nitropyridone 4-carboxylate (9-1) 
To a slurry nitroacetamide ammonia salt (70.3 g, 581 mmol) in 400 mL of deionized water was added 100 g (633 mmol, 1.09 equiv.) of ethyl 2,4-dioxovalerate followed by a solution of piperdinium acetate (prepared by adding 36 mL of piperdine to 21 mL of acetic acid in 100 mL of water). The resulting solution was stirred at 40xc2x0 C. for 16 h then cooled in an ice bath. The precipitated product was filtered and washed with 50 mL of cold water to give the above pyridone 9-1 as a yellow solid. 1H NMR (CDCl3) xcex4 6.43 (s, 1H), 4.35 (q, J=7 Hz, 2H), 2.40 (s, 3H), 1.35 (t, J=7 Hz, 3H).
Step B: Ethyl 2-methoxy-6-methyl-3-nitropyridine 4-carboxylate (9-2) 
A solution of the pyridone 9-1 from step A (6.2 g, 27.4 mmol) in 50 mL of DCM was treated with 4.47 g (30.2 mmol) of solid trimethyloxonium tetrafluoroborate and the mixture was stirred at 40xc2x0 C. until the reaction was judged to be complete by HPLC (typically 24-72 h). The reaction mixture was concentrated to one-third volume, loaded onto a silica gel column and eluted with 2:3 EtOAc/Hexane to give the methoxy pyridine 9-2 as a yellow liquid. 1H NMR (CDCl3) xcex4 7.2 (s, 1H), 4.35 (q, J=7 Hz, 2H), 4.05 (s, 3H), 2.55 (s, 3H), 1.35 (t, J=7 Hz, 3H).
Step C: Ethyl 3-amino-2-methoxy-6-methylpyridine 4-carboxylate (9-3) 
To an oxygen free solution of the nitro ester 1-2 from step B (2.5 g, 10.4 mmol) in 50 mL of EtOAc was added 520 mg of 10% Pd on charcoal. Hydrogen gas was added and the reaction mixture was stirred for 17 h. The solution was filtered through a pad of Celite, concentrated and chromatographed (2:3 EtOAc/Hexane) to give the desired amine 9-3 as a white solid.
1H NMR (CDCl3) xcex4 7.05 (s, 1H), 5.70 (bs, 2H), 4.35 (q, J=7 Hz, 2H), 3.95 (s, 3H), 2.37 (s, 3H), 1.39 (t, J=7 Hz, 3H).
Step D: Amino alcohol 9-4
To a xe2x88x9270xc2x0 C. solution of 260 mg (1.0 mmol) of the ester 1-3 from step C in 5 mL of THF was added 1.2 mL (3.5 mmol) of 3 M MeMgBr. The resulting solution was allowed to warm to ambient temperature over 16 h. The reaction mixture was quenched with 5 mL of saturated NH4Cl solution and the two phases were separated. The aqueous phase was extracted with 10 mL of EtOAc and the combined organic extracts were washed with 5 mL of brine and dried over MgSO4. The yellow solution was concentrated and chromatographed (1:1 EtOAc/Hexane) give alcohol 9-4. 1H NMR (CDCl3) xcex4 6.45 (s, 1H), 4.60 (bs, 1H), 3.95 (s, 3H), 2.55 (s, 3H), 1.60 (s, 6H).
Step E: Oxazinone 9-5
To a solution of 386 mg (2.0 mmol) of the amino alcohol 9-4 from step D in 10 mL of TBF was added 1.62 g (10.0 mmol) of 1,1xe2x80x2-carbonyl diimidazole. The resulting solution was heated at 55xc2x0 C. over 16 h. The reaction mixture was cooled and the solvent was removed by rotory evaporation. The mixture was redissolved in 50 mL of EtOAc and washed sequentially with 10 mL each of saturated NH4Cl solution, water, then brine. The solution was concentrated and chromatographed (1:1 EtOAc/Hexane) to give oxazinone 9-5. 1H NMR (CDCl3) xcex4 7.17 (bs, 1H), 6.49 (s, 1H), 3.95 (s, 3H), 2.40 (s, 3H), 1.66 (s, 6H).
Step F: Pyridone 9-6
To 333 mg (1.5 mmol) of the oxazinone from step E was added 1.72 g (15.0 mmol) of solid pyridine hydrochloride. The solid mixture was heated at 155xc2x0 C. for 5 min to effect a melt. The reaction mixture was cooled to rt, quenched with 10 mL of water and stirred for 20 min. The resulting precipitate was filtered and air dried to give pyridone 9-6. 1H NMR (DMSO d6) xcex4 11.85 (bs, 1H), 9.30 (bs, 1H), 6.03 (s, 1H), 2.10 (s, 3H), 1.45 (s, 6H).
Step G: Benzyl Ester 9-7
To 186 mg (0.89 mmol) of the pyridone 9-6 from step F in 5 mL of DMF was added 325 mg (1.0 mmol) of Cs2CO3 and 0.158 mL (1.0 mmol) of benzyl 2-bromoacetate. The resulting mixture was stirred at rt for 15 h. The reaction mixture was then evaporated to dryness, redissolved in 20 mL of EtOAc and washed with 3xc3x975 mL of brine. The organic solution was dried over MgSO4 concentrated and chromatographed (EtOAc) to give benzyl ester 9-7. 1H NMR (CDCl3) xcex4 7.45 (bs, 1H), 7.40-7.20 (mn, 5H), 5.90 (s, 1H), 5.25 (s, 2H), 4.82 (s, 2H), 2.30 (s, 3H), 1.65 (s, 6H).
Step H: Carboxylic Acid 9-8
A solution containing 176 mg (0.492 mmol) of the ester 9-7 from step G and 50 mg of 10% Pd on carbon in 12 mL of THF and 6 mL of MeOH was hydrogenated at room temperature under a balloon of H2. After stirring for 20 min, the reaction mixture was filtered through Celite and evaporated to dryness to give acid 9-8. 1H NMR (DMSO d6) xcex4 13.2 (bs, 1H), 9.45 (s, 1H), 6.20 (s, 1H), 4.70 (s, 2H), 2.50 (s, 3H), 1.60 (s, 6H).
Alternative intermediates, where R1 and R2 are other than methyl, may be prepared according to a procedure similar to the one outlined above but reacting 9-3 with an alternative reagent, such as EtMgBr instead of MeMgBr.
Scheme J outlines a procedure for using the intermediate formed according to Scheme I to make a final active compound of the invention. 